With the increase in the packing density of LSI (large scale integration) and other circuits, pattern miniaturization of internal circuits is advanced. This leads to the increase of interconnect resistance due to the decrease in interconnect cross-sectional area. Furthermore, the spacing between adjacent interconnects is narrowed, and hence the capacitance between interconnects is increased. This increases the interconnect delay time determined by the interconnect resistance and the interconnect capacitance.
As a technology for solving the problem of interconnect delay associated with the increased density of LSI and other circuits, optical interconnect technology for replacing electrical signals by optical signals is drawing attention. Optical interconnect technology is a technique for signal transmission using optical waveguides instead of metal interconnects. Signal transmission using optical waveguides does not involve the aforementioned increase in the interconnect resistance and the capacitance between interconnects associated with miniaturization. Thus, further acceleration of operating speed is expected. In such optical interconnect technology, further improvement in the transmission efficiency of optical signals is required.